1. Field of the Invention
The present invention relates to a cooling, heating or drying system for strips of material such as metal strips and, more specifically, it relates to such a system which is adapted for high speed, thermally efficient processing of metal strip.
2. Description of the Prior Art
It has long been known that for many purposes a combination of materials may provide an advantageous blend of properties for a given product. Among such combinations are the coating of steel strip with a relatively thin layer of zinc in a galvanizing process.
In respect of continuous galvanizing, a steel coil provides a continuous strip which is, in one embodiment, immersed in a molten bath of zinc, is passed through a furnace and is subsequently cooled prior to recoiling. Various types of cooling means for such systems have been known. See, generally, Metal Producing, July, 1990, pages 33, 53.
It has been known in the galvanizing art to employ elongated cooling tubes having longitudinal slots therein. Such tubes are positioned relatively close to the strip being cooled, e.g., on the order of about 5 inches. A number of problems have arisen from such constructions. More specifically, the close proximity of the slots to the strip has resulted in inefficient air flow as the spent gas which has already had contact with the strip surface tends to be re-entrained or interfere with efficient flow of the cooling gas from the slots to the strip surface. Also, occasionally either the strip or the slotted tube would be damaged as a result of undesired contact therebetween.
A general disclosure of the use of plates with orifices or jet tubes in heating, cooling, or drying of various industrial products is contained in Jet Impingement Heat Transfer From Jet Tubes in Orifices, National Heat Transfer Conference, 1989, HTD-Vol. 107, pages 43-50. While not specifically directed toward the cooling of metal strip, the concept of multiple jets for impinging air on a plate and exhausting such air is discussed.
A further problem encountered in respect of cooling lines for galvanized steel process systems, is the fact that the desire for increased productivity has resulted in the need for enhanced cooling systems, but existing plant structures frequently are not adequately sized to permit installation of the equipment needed for such enhanced cooling.
There remains, therefore, a very real and substantial need for improved cooling, heating and drying systems for elongated strip materials such as may be employed in metal strip lines, such as galvanizing lines.